Outflow Water Quality Research Articles

Is water replenishment an effective way to improve lake water quality? Case study in Lake Ulansuhai, China

Lakes are an important component of the global water cycle and aquatic ecosystem. Lake water quality improvement have always been a hot topic of concern both domestically and internationally. Noncompliant outflow water quality frequently occurs, especially for lakes that rely mainly on irrigation return flow as their water source. External water replenishment to improve the water quality of lakes is gradually being recognized as a promising method, which however, is also a controversial method. Lake managers, in the case of constant controversy, hesitate about the appropriateness of lake water replenishing. Thus, taking Lake Ulansuhai in China as an example, this study aimed to construct a lake hydrodynamic and water quality model, under the constraint of multiple boundary conditions, that has sufficient simulation accuracy, and to simulate and analyze the changes in COD (Chemical Oxygen Demand) and TN (Total Nitrogen) concentrations in the lake area before and after water replenishment, and explore whether water replenishment was an effective method for improving lake water quality. The results showed that when the roughness value of Lake Ulansuhai was 0.02, the TN degradation coefficient K was 0.005/d, and the COD degradation coefficient K was 0.01/d; the simulation and measured values had the best fit, and the built model is reasonable and reliable can be used to simulate lake water quality changes. By external water replenishment lasting 140 days in the water volume of 4.925 × 108 m³, the COD and TN concentrations in Lake Ulansuhai could be stabilized at the Class V water quality requirement, which helped improve the self-purification ability of the lake area. Water replenishment was proved to be an effective method for improving the water quality of the lake, but water replenishment is only an emergency measure. Lake water replenishment is more applicable to areas with abundant water resources. External source control and internal source reduction of lake pollution and protection of lake water ecology are the main ways to improve lake water quality for water-deficient areas under the rigid constraints of water resources. In the future, key technologies for reducing and controlling pollution in irrigation areas, construction of lake digital twin platforms, and active promotion of lake legislation work should be the main research direction for managing the lake water environment.

Evaluation of pollutant removal efficiency of urban stormwater wet ponds and the application of machine learning algorithms

Wet ponds have been extensively used for controlling stormwater pollutants, such as sediment and nutrients, in urban watersheds. The removal of pollutants relies on a combination of physical, chemical, and biological processes. It is crucial to assess the performance of wet ponds in terms of removal efficiency and develop an effective modeling scheme for removal efficiency prediction to optimize water quality management. To achieve this, a two-year field program was conducted at two wet ponds in Calgary, Alberta, Canada to evaluate the wet ponds' performance. Additionally, machine learning (ML) algorithms have been shown to provide promising predictions in datasets with intricate interactions between variables. In this study, the generalized linear model (GLM), partial least squares (PLS) regression, support vector machine (SVM), random forest (RF), and K-nearest neighbors (KNN) were applied to predict the outflow concentrations of three key pollutants: total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP). Generally, the concentrations of inflow pollutants in the two study ponds are highly variable, and a wide range of removal efficiencies are observed. The results indicate that the concentrations of TSS, TN, and TP decrease significantly from the inlet to outlet of the ponds. Meanwhile, inflow concentration, rainfall characteristics, and wind are important indicators of pond removal efficiency. In addition, ML algorithms can be an effective approach for predicting outflow water quality: PLS, GLM, and SVM have shown strong potential to capture the dynamic interactions in wet ponds and predict the outflow concentration. This study highlights the complexity of pollutant removal dynamics in wet ponds and demonstrates the potential of data-driven outflow water quality prediction.

Importance of water level management for peatland outflow water quality in the face of climate change and drought

The impact of different climate scenarios, drought, and water level management on the outflow water quality of peatlands has been investigated. A mesocosm experiment has been conducted within climate control chambers to simulate current (2016–2019 real-time) and future representative concentration pathway (RCP) climate scenarios (RCP 2.6, 4.5 and 8.5). To assess the efficiency of a management strategy for improving peatland water quality, water level adjustment was applied to half of the system at the same time for each climate scenario. Furthermore, the mesocosm experienced the 2018 European drought during the simulation years, and the corresponding impact was analyzed. The results of this study revealed a substantial and favorable impact of water level management on water quality of peatlands under different climate scenarios. The effect of water level management was the largest for ammonium (NH4-N) and 5-day biochemical oxygen demand (BOD5), and the smallest for total phosphorus (TP). Drought had a strong impact on chemical variables, increasing their concentration and deteriorating the water quality of peatland outflow. However, water level management can stabilize the nutrient levels in peatland outflows, particularly during drought and under warmer climate scenarios, thus mitigating the adverse effects of climate change.

Dynamics of radiocesium in an irrigation reservoir managed at low water level from the perspective of inflow and outflow water quality under non-flood conditions

Dynamics of radiocesium in an irrigation reservoir managed at low water level from the perspective of inflow and outflow water quality under non-flood conditions

Ranking Three Water Sensitive Urban Design (WSUD) Practices Based on Hydraulic and Water Quality Treatment Performance: Implications for Effective Stormwater Treatment Design

Bioretention basins, constructed wetlands and roadside swales are among the most common Water-Sensitive Urban Design (WSUD) or stormwater quality treatment systems. Although these systems can reduce stormwater quantity and improve quality, their hydraulic and water quality treatment performances are different. The aim of this study was to investigate the hydraulic and water quality performance of a bioretention basin, a constructed wetland and a roadside swale by analyzing monitored water quantity and quality data from a range of rainfall events using a ranking approach. The study outcomes showed that a bioretention basin performed better in relation to peak flow and runoff volume reduction while the constructed wetland tended to produce better outflow water quality. The roadside swale had a relatively lower capacity for treating stormwater. These results suggest that a bioretention basin could be the preferred option when the primary requirement is water quantity improvement. However, if water quality improvement is the primary consideration, a constructed wetland could be more efficient. Additionally, when designing a treatment train, it appears to be preferable to place a bioretention basin prior to a constructed wetland. Further, a swale appears to be more appropriate for use as a pretreatment device. The research study outcomes will contribute to effective stormwater treatment design.

Integrating Tank Model and adsorption/desorption characteristics of filter media to simulate outflow water quantity and quality of a bioretention basin: A case study of biochar-based bioretention basin

Reliable approaches for accurately assessing the performance of stormwater treatment systems is essential for their effective design, including filter media selection which can be a significant constituent in stormwater treatment systems. This study presents an innovative modelling approach integrating the Tank Model with the adsorption-desorption characteristics of the filter media. The resulting modelling approach was applied to simulate a field-scale bioretention basin where biochar was used as filter media with over ten years of rainfall records. The resulting outflow and overflow volumes were compared with observed data for calibration. The Stormwater Treatment Tank Model (STTM) was validated using the Leave-One-Out-Cross-Validation (LOOCV) method. The simulation outcomes include water outflow and overflow (quantity) from the bioretention basin as well as outflow water quality represented by three heavy metals (Pb, Cu, and Zn). The modelling approach developed was found to be capable of accurately simulating outflow and overflow volumes, with outlet water quantity being significantly influenced by the total rainfall depth. The modeling results also suggested that a sole treatment system would not be adequate, particularly for large rainfall events (>100 mm) and a treatment train would be more effective. Simulating long-term (over ten years) pollutant removal performance in the bioretention basin indicated that heavy metals outflow event mean concentration (EMCs) values calculated using simulated results of 30% biochar application rate generated the best pollutant removal with consistent values (2.7 μg/L, 3.0 μg/L, 17.2 μg/L for Pb, Cu, and Zn, respectively). These results confirm that the modelling approach is reliable for assessing long-term treatment performance, as well as a robust tool able to contribute to more effective treatment system design, particularly filter media selection and evaluation.

An adaptive surrogate-based, multi-pollutant, and multi-objective optimization for river-reservoir system management

Integrated management of quality and quantity of river-reservoir water can provide comprehensive information to manage river-reservoir water resources. However, high computational bottlenecks have prevented such management from being applicable in real-world systems. Accordingly, in the present study, we proposed a multi-objective optimization algorithm based on modular support vector regression (SVR) in which several small sub-SVR modules trained through an efficient adaptive procedure cooperate to solve a large-scale problem related to integrated management of quality and quantity of river-reservoir. The performance of the proposed approach was evaluated through an adaptive surrogate-based simulation-optimization (ASBSO) framework under reservoir selective withdrawal scheme (SWS) in Ilam integrated River-Reservoir. The ASBSO framework provided a set of non-dominated optimal solutions to alleviate Ilam River water quality standard violations, enhance Ilam Reservoir outflow water quality, and maximize the downstream water supply satisfaction. The analysis of the Pareto-front indicated that the implementation of MPWLA (multi-pollutant waste load allocation) programs at any level could alleviate the water quality problems in Ilam Reservoir. Furthermore, the reservoir water storage in the regular patterns to meet downstream water demands have resulted in water quality deteriorations in Ilam Reservoir. The results obtained from examining the proposed approach, showed that integrated river-reservoir system management improved water quality in the range from 7 to 28% at the checkpoints of the Gol-Gol Branch of Ilam River and in the range from 5 to 21% at Ilam Reservoir outflow.

Assessment of Low-Impact development for managing aquatic ecosystem

Urban aquatic life communities are among the most endangered species in the United States, and their decline has been linked to pollutants and sediments from urban development. Low Impact Development (LID) practices were applied to manage urban stormwater runoff as part of green infrastructure. However, there remains a debate regarding the role played by LIDs in protecting aquatic life due to a lack of large-scale evidence. Given this knowledge gap, a Sub-hourly time step SWAT (Soil Water Assessment Tool) model was calibrated and validated to evaluate the potential impact of LID practices on aquatic life in the Blunn Creek Watershed in Austin-Texas.The evaluation of LID practices performance was based on (i) incorporating and representing these practices into the SWAT model, (ii) studying output flows, and (iii) assessing watershed hydrological responses and their impact on aquatic life communities. Several measures such as reduction in peak flows, increasing both baseflows, and Aquatic Life Potential (AQP) values were used to assess flows coming out of LID practices. The types of LIDs considered were raingarden, permeable pavement and detention pond.Results showed that a combination of permeable pavement and raingarden resulted in the greatest percentage of increase in AQP values and baseflows and the greatest reduction in peak flows. The detention pond had the least percentage increase in AQP and baseflows as well as the least percentage of reduction in peak flows. The findings of this study are likely to be of interest to policymakers. LIDs are efficient applications on a watershed scale and could contribute to reduce total runoff and enhance outflow water quality. This study provides an in-depth discussion over the latest essence of LID technologies, which magnify their capabilities to control stormwater, while also protecting urban aquatic life. Cities and developers should encourage the development of green cities using LID technologies.

Multivariate assessment of outflow water quality in highly urbanized creek system: implication of natural and anthropogenic processes.

Nutrient source and transport study in tropical creeks adjacent to megacities are sparse on a regional and global scale. High-frequency chemical data collected during 2017-2018 in the Thane creek system, the largest micro-tidal urbanized creek in Asia, were analysed to assess the chemical water quality, with its linkage to different hydrological stages (southwestmonsoon, post- and pre-monsoon) and ongoing anthropogenic activities. Cluster analysis indicates typical zonation between creek outflow and nearshore waters with distinctive physicochemical properties. The creek outflow upholds substantial amounts of nutrient and suspended sediment due to turbid water movement from the ephemeral mudflats and anthropogenic dredging. The year-round hyper-turbid condition in the bottom water triggers the addition of disproportionate nutrients (9% dissolved inorganic nitrogen (DIN) and 14% reactive phosphorous (PO43-) in the outflow region. The DIN and PO43- removal up to 10 and 35%, respectively, occurs in the nearshore region; sedimentation, which acts as a sinking interface for nitrogen and phosphorous, also causes shifting in their limiting conditions. The hyper-turbid condition causes removal of dissolved silicate (DSi) by 5% in the entire region. Ammonium (NH4+)is mainly sourced from the sewage in outflow watersand efficiently mineralized. Chemical indexing of water highlights that the bottom water column remained un-supportive to the balanced ecology. The findings of this study have implications for other tropical creek-estuary concerning management strategies against inadequate flushing. The stalled nutrient export affected balance ecology in tropical Thane creek, which need attention in order toaccurately understand the impact onadjacent marine environment and toform effective mitigation policies.

Quantifying the contributions of structural factors on runoff water quality from green roofs and optimizing assembled combinations using Taguchi method

Runoff water quality of green roofs often comes under debate, and the mechanism of runoff pollution retention is still unclear. How to quantify the influencing contributions of structural factors to runoff pollution of green roofs and optimize the assembled combinations for improving water quality are ambiguous. In this study, runoff plots of extensive green roofs with Taguchi designed structural factors and levels were constructed and simulated rainfall experiments were conducted. Influences of structural factors on outflow water quality of green roofs were statistically assessed and quantified. Runoff water quality of green roofs with assembled combinations at specific levels were optimized and predicted by using the Taguchi method. Results showed that except for the pH and NO3– concentrations, the extensive green roofs acted as a source of the tested pollutants in stormwater runoff. Contributions of substrate materials on pH, EC, ESP (exchangeable sodium percentage), F−, NO3– and NO2-N concentrations were the highest among the structural factors, and contribution percentages ranged from 33.38% to 64.47%. The vegetation types had important contributions on Cl−, SO42− and TP concentrations, and the contribution percentage was 74.72%, 71.23% and 45.16% respectively. Influences of substrate depths and slope gradients on outflow water quality were small. Most of the determination coefficients (R2) of regression analysis between the measured and predicted water quality parameters under Taguchi design were ranged from 0.843 to 0.997. Except the pH and NO3– parameters, the Taguchi predicted water quality under the optimum conditions were improved by 10.2–77.6%. These results will aid understanding of the retention mechanism of green roofs on runoff pollutants and improving runoff water quality through the optimization of green roof design.

Metal leaching and toxicity of denitrifying woodchip bioreactor outflow—Potential reuse application

The denitrifying woodchip bioreactor is designed to remediate nitrate-rich water, including those produced from aquaculture effluents. Reuse of treated bioreactor outflows in recirculating aquaculture would offer considerable water savings and valuable alkalinity recuperation. However, such bioreactors may leach detrimental wood-bound contaminants, preventing outflow reuse. To determine water reuse potential, woodchip media from two hardwood species (white ash, Fraxinus americana; Norway maple, Acer platanoides) were evaluated for 206 d under a range of operating conditions (start-up, steady-state, reducing conditions, and drying-rewetting cycles) for a spectrum of potentially harmful dissolved contaminants. Aerated outflows also were evaluated for acute and chronic toxicity to the biologically sensitive invertebrate Ceriodaphnia dubia. Dissolved metal leaching subsided within the first few weeks of operation, though initial concentrations of copper and zinc were detected at concentrations of concern. Elevated concentrations of tannins-lignin and total ammonia nitrogen were detected throughout the study and were influenced by operational phase. Acute toxicity was not generally detected, though chronic toxicity was observed during drying-rewetting cycles in the maple outflows. The measured toxicity was not correlated with water chemistry, indicating an additive effect of several toxicants. Overall, significant differences in outflow water quality between ash and maple wood species were negligible. Results indicated that bioreactor outflows may be applicable for aquacultural reuse, though reusing outflows immediately following start-up or restarting after a dry period would not be recommended.

Correlation Analysis of Water Quality Between Lake Inflow and Outflow: A Case Study of Poyang Lake

The relationships between inflow and outflow water quality data for Poyang Lake from 1996 to 2016 are discussed and the main influencing factors are identified. TN and TP were the main factors causing a decline in water quality in Poyang Lake during the study period. The water quality of both the inflow and outflow rivers was generally good between 1996 and 2003; however, water quality declined over the study period, which is attributed to an increase in nutrients loads in the watershed. From 2004 to 2011, the water quality of the "Five Rivers" decreased significantly, which caused the water quality of Poyang Lake to decline. Due to the high purification capacity of Poyang Lake, the water quality of the outflow during this period was relatively good. A decline in water quality after this point was affected by pollution loads and hydrological conditions. Specifically, from 2012 to 2016, water quality in Poyang Lake and of the inflow water declined further. This was combined with a decrease in the water-purification capacity of the lake due to changes in the hydrological conditions, resulting in lower water quality at the outflow. Overall, the water quality of the inflow river has been closely related to the water quality in Poyang Lake. The concentrations of TN were significantly higher in the southern and eastern areas of Poyang Lake compared to the western areas. Higher nutrient loading from the Ganjiang River and the Xinjiang River has been an important driver. The concentrations of TP in the southern area of the lake have been significantly higher than in the eastern and western areas. This is attributed to comparatively high TP loads in the Ganjiang River and the Fuhe River. Compared to the changes in hydrological conditions, variations in nutrient loading have had a greater effect on water quality in the lake.

PIV experimental study on the flow characteristics upstream of a floating intake in nonlinear stratified ambient conditions

Selective withdrawal is commonly implemented in nonlinearly stratified ambient, which typically has stratified ambient conditions, for purposes of controlling quality. A floating intake is applied as an effective facility of selective withdrawal. However, the outflow dynamics of a floating intake in a nonlinearly stratified ambient have been disregarded, which has a significant effect on the outflow water quality of a reservoir. Experiments were conducted to investigate the effect of thermal stratification on the flow characteristics using particle image velocimetry at three temperature distributions (no stratification, weak stratification and strong stratification). The flow fields upstream of the floating intake showed that the withdrawal layer was formed inhibited by the thermal stratification. And strong stratification produced the thinner withdrawal layer thickness, leading to a larger nonuniform coefficient of the velocity profile. To quantitatively describe the velocity profiles, formulas of dimensionless velocity profiles were proposed. The flow developments were analysed, and the virtual control points located 0.56d above the floating intake (where d is the straight pipe diameter of the floating intake) were obtained. The positions of virtual control points mainly depended on the withdrawal discharge. The decay rate of the velocity along the horizontal line passing through the virtual control point was inversely proportional to the stratification intensity.

Enhancing Escherichia coli removal in stormwater biofilters with a submerged zone: balancing the impact of vegetation, filter media and extended dry weather periods

ABSTRACTStormwater biofilters have shown promising yet variable removal of faecal microorganisms. The effects of vegetation, filter media and extended drying on the removal of Escherichia coli are investigated in the current study. Semi-synthetic stormwater was applied to 25 biofilters representing five different design configurations, all of which contained a submerged zone (SZ). The influence of extended dry periods on E. coli removal depended on the presence/absence of vegetation. Uptake of SZ water by plants with extensive roots during the dry periods lead to deterioration of the subsequent outflow water quality compared to unvegetated biofilters. Without a significant loss of SZ volume, a loamy sand biofilter planted with either Carex appressa or Leptospermum continentale can achieve a higher removal performance than an unvegetated washed sand biofilter. However, in warmer climates that experience long dry weather periods, and inability to control SZ volumes, un-vegetated columns may result in lower effluent E. coli concentrations.

Impact of pH on the Treatment of Artificial Textile Wastewater Containing Azo Dyes Using Pond Systems

Two controlled experiments were operated to evaluate the impact of pH on the treatment efficiency of azo dyes within artificial textile wastewater using ponds as a polishing step. The objectives were to assess the (1) inflow water quality; (2) the presence of Lemna minor and the algae Oedogonium spp. on the dye removal and the outflow water quality; and (3) suitability of applying artificial textile wastewater and the impact of this wastewater and the dye on plants. Findings indicate that the shallow ponds planted with L. minor and/or algae treated the dye Basic Red 46 (BR46) significantly (p < 0.05) higher than the control ponds without any significant (p > 0.05) impact of pH. The potential of L. minor and algae for removal of BR46 was 31% and 25%, respectively. The removal of BR46 was around 89% for ponds planted with L. minor and algae, 58% for algae ponds and 33% for control ponds. Wetlands with L. minor are successful and economic in the complete degradation of BR46 at concentrations of 10 mg L−1 for any pH value between 6 and 9. The removal of ammonium-nitrogen (NH4-N), nitrate-nitrogen (NO3-N) and ortho-phosphate-phosphorus (PO4-P) was higher in planted than in unplanted ponds. The mean outflow values of chemical oxygen demand, NH4-N, NO3-N, suspended solids and total dissolved solids were within the limits for safe discharge. The artificial wastewater constituents after dilution (1 part of artificial wastewater to 24 parts of raw water) were suitable to use within the treatment system containing L. minor.

Influence of Vegetation on Long-term Phosphorus Sequestration in Subtropical Treatment Wetlands.

Sustainable operation of a treatment wetland depends on its continued treatment of influent water to achieve desired outflow water quality targets. Water treatment or nutrient reduction is attained by a combination of biotic and abiotic processes. We studied one of the world's largest treatment wetlands established to revive the Florida Everglades from impacts of excessive phosphorus (P) inputs. Phosphorus retained in the treatment wetlands is sequestered within the accumulated material via biotic and abiotic pathways that are influenced by the existing wetland vegetation. Recently accreted soils (RAS) provide a major sink for stored P, and long-term P removal efficiency of treatment wetlands is governed by the stability of accreted P because more stable P pools are less susceptible to mobilization and loss. We quantified reactive P (extracted with acid and alkali) and nonreactive P (not extracted with acid and alkali) pools in wetland soils by using an operationally defined P fractionation scheme and assessed the effect of emergent vs. submerged vegetation communities on stability of sequestered P. Reactive P comprised 63 to 79% of total P in wetland soils without a clear difference between two vegetation groups. The quantities of reactive P forms (inorganic vs. organic P) were significantly different between two vegetation types. A higher proportion of reactive P was stored as organic P in flocculent detrital organic matter (floc) and RAS under emergent vegetation (46-47% total P) in comparison with submerged vegetation (21-34% total P). The dominant P removal pathway in the submerged vegetation system was associated with calcium whereas plant uptake and peat burial appeared to be the main pathway in the emergent vegetation system.

Modeling phosphorus retention at low concentrations in Florida Everglades mesocosms

Reducing phosphorus (P) concentration in surface water is a primary component of the ongoing effort to restore the Florida Everglades. Engineered wetlands are currently being used to retain P from stormwater inflows but are not consistently achieving outflow P concentration goals. A three-year mesocosm study was performed investigating the effects of different plant communities on P retention within engineered wetlands. A dynamic model was constructed in the high-level simulation software STELLA, using water, soil, weather, and plant data from this mesocosm study. The model consists of three interconnected submodels: plant growth, hydrology, and P dynamics. The model simulates processes in water and soil related to all four forms of P: dissolved organic, dissolved inorganic, particulate organic, and particulate inorganic. Model verification and subsequent calibration was performed using biweekly outflow water quality data from a mesocosm containing a submerged aquatic vegetation (SAV) community consisting of Najas guadalupensis and the algae Chara sp. Model validation was then conducted using data from separate mesocosms with three different plant communities: monocultures of Typha domingensis or Cladium jamaicense, and a combination of Nymphaea odorata and SAV. The model was able to simulate outflow concentrations of total phosphorus from all four plant communities with average relative errors of less than 35%. A sensitivity analysis revealed the relative importance of the various processes involved in the retention of all P forms and the effects of different vegetation communities on these processes. Further simulations were run to predict the outflow total P concentrations for an additional year beyond the end of the mesocosm study.

Colonization of Microbial Biofilms in Pipeline of Water Reuse

Aim of this study was to investigate biofilms attached in pipeline of water reuse from the MBR system treating sewage without chlorination in correlation to the outflow water quality. Two general pipe materials: polyvinyl chloride (PVC) and polyethylene (PE) were employed in the experiment. The peak growths were found at week 4 in both pipes. The maximum biofilms in PE pipe was 33 mgVSS/cm 2 with the growth rate of 4.75 mgVSS/cm 2 -d which was significant higher than that of PVC pipe. Biofilms examined by PCR-DGGE technique revealed five bacterial species in PE biofilms namely Sinorhizobium medicae WSM419, Sinorhizobium fredii NGR234, Geobacter sp. M18, Parachlamydia acanthamoebae UV-7, and Mycobacterium chubuense NBB4. The VSS concentrations in outflow had directly correlated to the biofilm attachment and detachment. High COD concentrations of outflow appeared during biofilm detaching phase. In summary, water quality of reuse water corresponded to the biofilms attachment and detachment in the pipeline.

Characterization and field test of an in situ multi‐platform optical sensor

The characterization and field testing of a compact in situ optical instrument using fluorescence, absorbance, and scattering to identify and quantify contaminants and natural substances in water bodies are described. The instrument, based on a technology named LEDIF (LED‐Induced Fluorescence) developed by Ng et al. (2012a) was configured for in situ long‐term continuous monitoring at a fixed location. The optical performance and sensing capabilities of the instrument were assessed by calibrating against laboratory‐prepared and commercial standards, and compared with several commercial sensors and published values. The effects on sensor response of temperature, pressure, and particle interference due to turbidity and total suspended solids were assessed and reported. Instrumental baseline shift over time, instrument detection limits, and the capability of LEDIF to determine characteristics such as quantum yield and intramolecular deactivation of fluorescence response, were also assessed. Experimental results match well with results from commercial instruments and published data. To demonstrate field deployment, the LEDIF instrument was installed at Chinese Garden of Singapore for longterm continuous monitoring of chlorophyll a (Chl a) and turbidity at a management‐selected location. The analytes were chosen based on management's needs in recording temporal trends of algal biomass and water cloudiness to develop effective controls of inflow and outflow water quality. A monitoring record showing the temporal response of algal biomass to ambient conditions and turbidity variations is presented and discussed.

A Study on Acclimation and Culture of Salt Tolerant Sludge

The inoculated sludge in this experimental system is from the end of aeration tank of the wastewater treatment plant. Under stable operation, the system’s treatments of COD and NH4+-N are all in line with Level One Urban Sewage Discharge stipulated by Pollutant Discharge Standards for Urban Sewage Treatment Plants (GB 18918-2002). The removal rates of COD and NH4+-N are 94.27% and 91.03%. By gradually improving the method of salinity acclimation, the salt tolerant sludge with outstanding performance can be successfully acclimated, and each gradual increase in salinity scope is controlled at around 4 g/L. When the salinity is 1%, the removal rates of COD and NH4+-N reach to 92.09% and 70.13%. The salinity has significant impacts on microbial activity. With the increase in salinity, the dehydrogenase activity gradually decreases. Salinity has significant effects on protozoa. Paramecia and nematodes can be taken as the biological indicator of outflow water quality of brine waste.